My
research activities are in theoretical condensed matter physics. My
main interest is the investigation of strongly correlated quantum
mechanical many body systems, particularly their new collective
behavior emerging due to competing interactions. Using quantum
statistical mechanics and many body theory, I am working on phenomena
like superconductivity, quantum phase transitions, magnetism,
disordered systems and non-equilibrium dynamics as well as quantum
effects in glassy systems.

RESEARCH
HIGHLIGHTS

spin liquid formation and bond order close to a Mott
insulating state

We investigate the emergence of superconductivity
in doped or pressurized Mott insulators within the framework of
resonating valence bond states, where strong quantum fluctuations of
frustrated spins lead to unconventional pairing, superconductivity
and new inhomogeneous states. We find spin liquid behavior and
d-wave superconductivity in an organic charge transfer salt as
function of the interaction strength. We also predict
superconductivity upon hole doping of the Mott insulating valence
bond solid SrCu2(BO3)2 while no
superconductivity is expected for electron doping. Superconductivity
in the hole doped system is not(!) due to a delocalization of
existing singlets in the valence bond solid and is closely related
to a spontaneous emergence of inhomogeneous plaquette order.

We present a theory for superconductivity and charge Kondo
fluctuations, i.e., resonant quantum valence fluctuations by two
charge units, for Tl-doped PbTe. We show that Tl is very special as
it first supplies a certain amount of charge carriers to the PbTe-valence
band and then puts itself into a self-tuned resonant state to yield
a new, robust pairing mechanism for these carriers.

The cooperative rearrangement of groups of many molecules has
long been thought to underlie the dramatic slowing of liquid
dynamics on cooling towards the glassy state. For instance, there
exists experimental evidence for cooperatively rearranging regions (CRRs)
on the nanometre length scale near the glass transition. The random
first-order transition (RFOT) theory of glasses predicts that, near
the glass-transition temperature, these regions are compact, but
computer simulations and experiments on colloids suggest CRRs are
string-like. Here, we present a microscopic theory within the
framework of RFOT, which unites the two situations. We show that the
shapes of CRRs in glassy liquids should change from being compact at
low temperatures to fractal or 'stringy' as the dynamical crossover
temperature from activated to collisional transport is approached
from below. This theory predicts a correlation of the ratio of the
dynamical crossover temperature to the laboratory glass-transition
temperature, and the heat-capacity discontinuity at the glass
transition. The predicted correlation quantitatively agrees with
experimental results for 21 materials.

We show that the interplay of geometric criticality and quantum
fluctuations leads to a novel universality class for the percolation
quantum phase transition in diluted magnets. All critical exponents
involving dynamical correlations are different from the classical
percolation values, but in two dimensions they can nonetheless be
determined exactly. We develop a complete scaling theory of this
transition, and we relate it to recent experiments in La2Cu1-p(Zn,Mg)pO4.
Our results are also relevant for disordered interacting boson
systems.

Maxim Dzero (2003-2006, next position: postdoc, jointly at Rutgers University, New Jersey and
Columbia University, New York, recipient of a 2005- postdoctoral
fellowship of the Institute for Complex Adaptive Matter)

S. Grabowski, J. Schmalian
and K .H. Bennemann, Doping Dependence of the
Superconducting State of the cuprates, Proceedings
of the International Conference on Superconducting
Mechanisms and Materials, Bejing 1997, Physica C
282-287, 1775 (1997)